Discovery of Homo naledi

In the Rising Star cave system in South Africa, located about 48 kilometers (30 miles) north of Johannesburg, paleoanthropologists have unearthed an extensive collection of more than 1550 skeletal elements from at least 15 individuals that have been provisionally assigned to a new species of the genus Homo. The location in which these numerous fossils were found is a highly inaccessible chamber known as the Dinaledi ("Star") Chamber; hence, this previously unknown offshoot of the hominin family has been given the name Homo naledi. This discovery has provided the largest morphologically homogeneous assemblage of a single species of ancient hominins yet found in Africa. See also: Anthropology; Fossil; Physical anthropology

Although the age of these unique fossil specimens still needs to be determined scientifically, analyses indicate they are from a species having a stature and weight like those of small-bodied humans, as well as humanlike feet and hands. Some aspects of the skull and face look similar to those of humans, although other features (for example, the jawbone and teeth) are very primitive. Notably, though, the endocranial (brain) volume is less than half that of modern humans and is more derivative of what is seen in other early human ancestors, particularly the australopiths [members of the genus Australopithecus, best known from the 3.2 million-year-old "Lucy" fossil (Australopithecus afarensis)]. Based on the mixture of humanlike and primitive anatomical traits, the lead investigators hypothesize that the age of H. naledi may date back approximately more than 2 million years, which would place it among the earliest known species of Homo. If the dating and taxonomic assignment of the species prove accurate, then H. naledi would need to be included in the ancient timeline of human evolutionary history. See also: Australopith; Australopithecus sediba; Dating methods; Earliest hominins; Fossil hominids from Dmanisi; Fossil humans; Homo erectus; Homo floresiensis: further insights; Homo heidelbergensis

Another striking aspect of this discovery is the evidence that the skeletal remains were deliberately placed into the Dinaledi Chamber, which is possibly suggestive of some ritualistic or symbolic behavior by H. naledi. Because the chamber is located 30 meters (98 feet) underground and is extremely difficult to reach, a hypothesis of deliberate burial seems plausible, especially if one takes into account the unusually large numbers of specimens, the lack of signs of predation on the bones, and the environmental conditions within the chamber. If this burial was done purposefully over time, it would be an incredibly early instance of this type of thought and action, one that is not known to have appeared among hominins until more modern species, such as H. sapiens and the Neandertals. See also: Neandertals; Origins of symbolic behavior; Taphonomy

The excavations in the Dinaledi Chamber that revealed the remains of H. naledi were undertaken in November 2013 and March 2014. The chamber is part of an extensive network of limestone caves belonging to the Cradle of Humankind World Heritage Site. This area has been the source of extensive and remarkable hominin finds, including some of the oldest on record. The fossil discovery of H. naledi was officially made public in September 2015. Still, some researchers remain cautious and are not yet satisfied to reconfigure and add a new extinct member to the hominin family tree. See also: Cave; Human origins

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